Journal
GEOPHYSICAL RESEARCH LETTERS
Volume 49, Issue 8, Pages -Publisher
AMER GEOPHYSICAL UNION
DOI: 10.1029/2021GL097699
Keywords
heat wave; atmospheric blocking; Pacific Northwest; local wave activity; diabatic heating; latent heating
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Funding
- NSF [AGS1909522]
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The study investigates the meteorological and dynamical conditions that led to extreme heat in the Pacific Northwest from late June to early July 2021. It finds that an upper-level atmospheric blocking and surface cyclogenesis off the coast of Alaska contributed to the extreme heat event. The study also highlights the critical role of a localized non-diabatic source in the formation and strength of the blocking.
We investigate the meteorological and dynamical conditions that led to the extreme heat in the Pacific Northwest from late June to early July 2021. The extreme heat was preceded by an upper-level atmospheric blocking that snatched a warm pool of air from lower latitudes. A heat-trapping stable stratification ensued within the blocking anticyclone, raising the surface temperatures significantly. An upper-tropospheric wave breaking and the concomitant surface cyclogenesis off the coast of Alaska initiated the block formation. The regional local wave activity budget reveals that a localized diabatic source associated with this storm critically contributed to an enhanced zonal wave activity flux downstream, whose convergence over Canada drove the blocking. A simple reconstruction based on the observed wave activity budget predicts a 41 percent reduction in strength and a 10-degree eastward displacement of the block when the upstream diabatic source is reduced by just 30 percent.
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